Histogram myth, your thoughts!

signgrap wrote:Ari thanks for your response. Let me see if I got this right. Let's say I photograph a B/W image comprised of 255 steps from black to white, similar to the "monitor calibration strip" used by many photography sites. But instead of 17 steps typically used, there are 255 steps. The only thing appearing in the image are the steps, being careful to include the same amount of the starting and ending steps. So each value represented is exactly the same size. The resulting image would have 51 steps in each fifth of the histogram. If this histogram were viewed with no tone curve i.e. linear would the resulting display be a straight horizontal line with the same number of pixels in each section of the five section histogram? I realize that the camera histogram would look different since this has some type of curve applied.

Since histograms don't necessarily show the brightest areas accurately (because the histogram is generated from the embedded JPEG not the RAW file) you need to be conservative in how far to the right you push the exposure.

AJSJones wrote:I think Reichmann confused a lot of people with the explanation based on the (incorrect) "number of tonal levels in each part of the histogram" explanation. ETTR is a good approach but it is simply based on getting a bigger signal to noise ratio because of the bigger signal you record. Clearly, you don't want to blow any important highlights (like the image in ctein's example) or white feather detail so it must be used "properly". However, if you know your camera and know when it is telling you which parts of the image are about to blow out (the blinkies in a jpeg based on settings that you have confirmed by subsequent evaluation of the converted image ) then it will not compromise the highlights but will improve shadows.

Neil Fitzgerald wrote:

Since histograms don't necessarily show the brightest areas accurately (because the histogram is generated from the embedded JPEG not the RAW file) you need to be conservative in how far to the right you push the exposure.

Except the raw file will (always?) have more data in the bright areas than the derivative jpeg so a conservative approach is not needed for that reason. If it's ok in the jpeg you'll have spare room in the raw file.